1. Technical Field
The invention relates to an image forming apparatus, particularly, technology to supply toner to the electrophotographic image forming apparatus which forms images on the recording material.
2. Related Art
For copying machines, printers, facsimile machines, and multi-functional image forming apparatuses including functions of the machines stated above, particularly for electrophotographic image forming apparatuses, speedup and coloring are in progress.
In high-speed image forming apparatuses, since a large amount of toner is consumed, a toner storing section of a large capacity suitable for high-speed performance of the high-speed image forming apparatuses is needed, which tends to make the space used by the toner storing section in the apparatuses large. Further, also in color image forming apparatuses, the space used by a toner storing section that stores toners of four colors tends to be large.
In typical image forming apparatuses, a toner storing section is located in the vicinity of a developing device. Therefore, as the space used by the toner storing section becomes larger as described above, it becomes more difficult to dispose the toner storing section in the vicinity of the developing device, which is a problem.
In TOKKAI No. 2000-137376, it is disclosed that toner is supplied from a toner storing section to a developing device by conveying a mixed fluid of toner and air with the use of an air pump.
A method disclosed in TOKKAI No. 2000-137376 allows a toner storing section to be arranged at a position distant from a developing device, giving a wider choice of the location of the toner storing section, and thus, the problem of arranging a toner storing section with a large capacity or a toner storing section of color toner is solved.
In the invention disclosed in TOKKAI No. 2000-137376, a first pump for supplying toner and a second pump for returning air to a toner storing section are used.
A toner supplying device disclosed in TOKKAI No. 2000-137376 that supplies toner through toner conduits with the use of a pump, as described above, is suitable for high-speed image forming apparatuses and color image forming apparatuses, but, if the apparatuses are used for a long time, failure in toner conveyance may be caused. For example, it is possible that the conduit is clogged with toner, air leaks at a joint section of the conduits occurs, or toner gets aggregated in a toner conveyance system, causing a failure in toner conveyance.
In the case where such a conveyance failure occurs, if a pump continues to run, it may cause a trouble of the apparatus. That is, if the pump continues to run with a conveyance failure, the conveyance system may be clogged with toner to be an unrecoverable failure, resulting in a requirement of replacing conduits.
It is desired that the above described problem with a toner supplying device for supplying toner with a pump is solved so that an image forming apparatus provided with a detection system capable of early detection of failure in toner conveyance is offered.